Wick for oil dispensing apparatus

ABSTRACT

Apparatus for lubricating the heated fuser roll in a heated pressure xerographic fusing system. The apparatus includes an applicator roll for providing a film of oil to a wick assembly having a main wick contacting the fuser roll and an auxiliary wick contacting the applicator roll and the main wick at one end and an oil supply at the other end to dispense sufficient oil when the applicator roll is inoperative. The improvement is in the form of a sponge member inserted between the main wick, auxiliary wick, and applicator roll to limit the flow of oil onto the main wick thereby preventing oversaturation thereof.

[111 3,831,553 1451 Aug. 27, 1974 WICK FOR OIL DISPENSING APPARATUS [75]Inventor: Raghulinga R. Thettu, Webster,

[73] Assignee: Xerox Corporation, Stamford,

Conn.

22 Filed: Dec.ll, 1972 21 App1.No.:-313,7l9

[56] References Cited UNITED STATES PATENTS 4/1958 Springer et a1.101/1325 12/1966 Aser et a1. 432/60 7/1967 Cassano ct a1 432/603,716,221 2/1973 Gorka 118/60 Primary Examiner-Mervin Stein AssistantExaminer-4x0 Millstein [57] ABSTRACT Apparatus for lubricating theheated fuser roll in a heated pressure xerographic fusing system. Theapparatus includes an applicator roll for providing a film of oil to awick assembly having a main wick contacting the fuser roll and anauxiliary wick contacting the up plicator roll and the main wick at oneend and an oil supply at the other end to dispense sufficient oil whenthe applicator roll is inoperative. The improvement is in the form of asponge member inserted between the main wick, auxiliary wick, andapplicator roll to limit the flow of 01] onto the main wick therebypreventing oversaturation thereof.

2 Claims, 4 Drawing Figures PATENTED ME 2 7 [974 arm" 3 PATENTEDAUBZTIW3,831,553-

sum an: 5

This application relates to fusing systems and in particular to animproved lubricating apparatus for removing toner particles from thefuser roll of a heated pressure fusing system.

In the practice of xerography as described in U.S. Pat. No. 2,297,691 toChester F. Carlson, a xerographic surface comprising a layer ofphotoconductive insulating material affixed to a conductive backing isused to support electrostatic images. In the usual method of carryingout the process, the xerographic surface is electrostatically chargeduniformly over its surface and then exposed to a light pattern of theimage being reproduced to thereby discharge the charge in the areaswhere the light strikes the layer. The undischarged areas of the layerthus form an electrostaic charge pattern in conformity with theconfiguration of the original light pattern.

The latent electrostatic image can then be developed by contacing itwith a finely divided electrostatically attractable material such as apowder. The powder is held in image areas by the electrostatic chargeson the layer. Where the charge field is the greatest, the greatestamount of powder is deposited; where the charge field is least, littleor no material is deposited. Thus, a powder image is produced inconformity with the light image of the document or object beingreproduced. The powder is subsequently transferred to a sheet of paperor other surface and suitable affixed thereto to form a permanent print.

One typical device for fixing the toner particles to the backing sheetis by a heated pressure fuser roll system in which the copy sheet ispassed through the nip of a Teflon coated heated fuser roll and a backuproll as described in U.S. Pat. Nos. 3,256,002 and 3,268,351. In suchfusing systems, care must be taken to remove unwanted toner particlesfrom the heated fuser roll prior to its contact with the copy beingfused. If care is not taken to keep the fuser roll free of tonerparticles, these toner particles can build up on the face of the fuserroll and degrade the quality of the fix by removing the fusingproperties on the surface of the roll contacting the copy sheet andtoner images. Furthermore, such unwanted toner particles can be releasedfrom the fusing roll upon its subsequent contact with the image to fusetoner particles to the copy sheet in non-imaged areas. A wick isgenerally used to dispense silicone oil by gravity on the externalTeflon surface of the heated fuser roll by a pad overlying the heatedfuser roll.

While the gravity dispensing wick in pad form is satisfactory where thewick is elevated over the nip it is not altogether satisfactory in otherarrangements such as where the heated fuser roll is disposed as thebottom roll of the fusing system.

The instant invention is an improved wickingapparatus which improves theflow of oil onto the bottom roll of a heated pressure roll fusing systemdescribed in U.S. Pat. No. 3,718,!16, issued on Feb. 27, 1973.

It is therefore an object of the present invention to improve heatedpressure fusing systems.

It is another object of the present invention to improve lubricatingwick assemblies of high temperature stability for use with heatedpressure fusing systems.

It is another object of the invention to provide wicking assembliescapable of retaining oil over a long shutdown period against gravity.

It is still another object of the present invention to enhance thewicking properties of an oil dispensing wick.

It is still another object of the present invention to provide animproved oil wicking assembly which is compatible with silicone andconforms to objects.

It is still another object of the invention to provide an oil wickingassembly which has a main wick and an auxiliary wick to dispensesufficient oil to the main wick in the event that the main wickapplicator is inoperative without oversaturation of the main wick.

It is still another object of the present invention to minimizeunnecessary maintenance of copier/duplicator systems.

These and other objects of the instant invention are obtained by a newand improved lubricating wick assembly which comprises a main wick whichcontacts the heater fuser roll and an applicator roll and an auxiliarywick and sponge member which control the flow of oil onto the main wick.The auxiliary wick has one end extending below the oil supply level andthe other end in contact with the applicator roll and sponge memberwhich contacts the main and auxiliary wicks and applicator roll.

Further objects of this invention together with additional features andadvantages thereof will become apparent from the following detaileddescription of the embodiment of the invention when read in conjunctionwith the accompanying drawings wherein:

FIG. 1 is a schematic representation of an automatic xerographicreproducing machine incorporating a heated pressure fusing systemutilizing the improved oil dispensing apparatus of the presentinvention;

FIG. 2 is a side sectional view of the heated pressure fusing systemaccording to the present invention;

FIG. 3 is an isometric view of the wicking assembly; and

FIG. 4 is an exploded view of the substantially smooth fuzz-free lowersurface of the wicking assembly.

Referring now to the drawings as shown in FIG. 1 an embodiment of theinvention in a suitable environment such as an automatic xerographicreproducing machine. The automatic xerographic reproducing machineincludes a xerographic plate or surface 10 formed in the shape of adrum. The plate has a photoconductive layer or light receiving surfaceon a conductive backing journaled in a frame to rotate in a directionindicated by the arrow. The rotation will cause the plate surface tosequentially pass a series of xerographic processing stations.

For purposes of the present disclosure the several xerographicprocessing stations in the path of movement of the plate surface may bedescribed functionally as follows:

a charging station A which the uniform electrostatic charge is depositedonto the photoconductive plate; I

an exposure station B at which light or radiation pattern of. copies tobe reproduced is projected onto the plate surface to dissipate thecharge in the exposed areas thereof to thereby form a latentelectrostatic image of the copies to be reproduced:

a developing station C at which xerographic developing materialincluding toner particles have an electrostatic charge opposite to thatof the latent electrostatic image is cascaded over the latentelectrostatic image to form a powdered image in configuration of thecopy being reproduced;

a transfer station D which the powdered image is electrostaticallytransferred from the plate surface to a transfer material such as paperwhich is then passed through heated pressure fusing system according tothe present invention as will be described hereinafter; and

a drum cleaning and discharge station E at which the plate surface isbrushed to remove residual toner particles remaining thereon after imagetransfer and at which the plate is exposed to a relatively bright lightsource to effect substantially complete discharge of any residualelectrostatic charge remaining thereon.

Referring now in particular to FIG. 2 there is shown the heated pressurefusing system of the present invention which includes a heated fuserroll 16 and a backup pressure roll 18. F user roll 16 is a hollowcircular cylinder with a metallic core 20 and a Teflon layer 22. A lamp24 serves as a source of thermal energy and is located at the center ofthe fuser roll. Power to the lamp is controlled by a thermal sensorgenerally called a thermistor contacting the periphery of the fuser rollas described for example in U.S. Pat. No. 3,357,249. The backup roll 18is also a circular cylinder and is made up of a metal core 30 surroundedby a thick rubber layer 32 and also a Teflon layer 34 to prevent soakingsilicone oil into rubber layer 32 and subsequent swelling.

When the two rollers 16 and 18 are engaged as shown in FIG. 2 theapplied load deforms the rubber in the pressure roll to provide the nipwith a finite width. The copy sheet 40 electrostatically bearing thetoner images 42 on the other side thereof is brought into contact withthe nip of the rolls with the toner image contacting the fuser roll 16.For a given temperature of the fuser roll, the fusing rate will dependupon the contact arc length of the support material against the dwelltime, i.e., the time the toner image remains between the fuser roll 16and the backup roll 18. Dwell time can be varied either by changing thesurface velocity of the rolls or by varying the contact arc length andholding the speed of the roll the same. Contact arc length depends onthe softness of the rubber on backup roll 18 and on the amount ofpressure between the rolls 16 and 18. The mechanism for driving therolls for lowering and raising the rolls into contact can beaccomplished by any suitable means as that described for example in US.Pat. No. 3,291,466 or by a suitable mechanical camming device.

As a sheet of material is advanced between the rolls l6 and 18 the tonerimage on the support material will contact the peripheral heated surfaceof the roll 16 whereby the toner image becomes tackified and in thistackified condition the toner will tend to oflset on this roll exceptthat it is partially prevented from doing so by the Teflon coating onthe roll. it is by the lubricating wick assembly of the presentinvention which is used to apply a thin film of offsetting preventingliquid such as silicone oil to the Teflon surface 22 of the fuser roll16 that offset is prevented.

An oil applicator apparatus 45 includes lubricating wick assembly 48, anoil pan 50 for maintaining a supply of silicone oil 51 and an applicatorroll 52. The oil pan is loaded against the fuser roll by a spring actionmounting not described as details of the mounting form no part of thepresent invention. Applicator roll 52 is used to convey a thin film ofoil to the bottom face 55 of the lubricating wick assembly as theapplicator roll is rotated in the direction shown by the arrow.Desirably, the applicator roll 52 is driven by an oil dispenser motor 58which is energized during the fusing operation depending upon the numberof copies being produced. In accordance with thepresent inventionlubricating wick assembly 48 includes two different layers the presentwicking materials. One layer 62 is Teflon which contacts the surface ofthe fuser roll 16. Another layer 62 is made of Nomex which has itsunderside 55 in contact with the applicator roll 52. Both Teflon andNomex are trademarks of DuPont Corporation, Wilmington, Delaware. Layers62 and 64 are assembled in overlapping relationship and their ends areclamped between plates 66 and 68 which are secured by any suitable meanssuch as screws 70 as best shown in FIG. 3. Spring metal brackets 72 and74 serve to provide support and conforming characteristics to the fuserroll for the assembly. Tab portions are provided for facilitating thehandling of the lubricating wick assembly for insertion and removal ofthe assembly into and out of the fuser system. Teflon is used as theupper layer because it has high lubricating characteristics as well asthermal stability at elevated temperatures ranging up to 400 F andabove. Nomex is used as a lower layer because of thermal stability atelevated temperatures up to 400 F and above and due to its high oilretention characteristics.

In order to enhance the oil retention characteristics and also enabletrouble-free application of oil to the surface of the Nomex layer 64,the lower surface 55 is flame treated to burn all the loose fibers torender a reticulated pattern free of loose fibers as best shown in FIG.4. Burning should be sufficient to form the surface fibers into a porousmembrane or a finished pattern. It has been found that removal of thesefibers from the Nomex layer has enabled a high oil retention of thelayer while insuring that the applicator roll does not stall which isnormally the case where the layer is dry which is caused by oil leakingthrough loose fiber material. Since the applicator roll motor isdesirably of a lower power unit it is essential that there be no bindingbetween the Nomex layer and the applicator roll causing the motor tostall. It has been observed that with the fuzz and/or loose fibersremoved that motor stalling is prevented and high oil retentionqualities retained.

In accordance with the present invention, the oil dispensing apparatusutilizes an auxiliary wick 75 which may be made out of any suitablewicking material and which supplies oil to the wick assembly 48 througha sponge member 80. Suitable materials for the auxiliary wick areCorfam, Nomex and Dacron. Preferably the auxiliary wick material will beable to withstand high temperatures, as high as 400 F. The auxiliarywick is arranged so that it is touching the applicator roll and thesponge member which also contacts the applicator roll and wick assembly.Any suitable material may be used for sponge member 80. Preferredmaterials are hexa fluoropropylene, vinylidine fluoride or Vitonfluoroelastomer, a registered trademark manufactured by DuPontCorporation, Wilmington, Delaware, fluoro silicone rubber, urethanefoam, and mixtures thereof. The auxiliary wick is maintained in positionby support member 77 which is made of any suitable thermally conductivematerial and is secured in place by a holding member 80 supported on thebottom of the oil pan. Sponge member 80 has a cellular structure whichserve to ensure that oil flow to the main wick is controlled to preventoversaturation thereof. Support bracket 77 preferably is made of anysuitable thermally conductive material such as metal in order to enhancethe transfer of oil from the auxiliary wick to the applicator roll. Ithas been found that a temperature gradient may exist between theauxiliary wick and the applicator roll and hence a thermally conductivesupport member serves to minimize this temperature gradient. Theauxiliary wick 75 serves to bring the oil up to the applicator roll to alevel such that upon rotation of the roll during onehalf of one copytime, the oil contacts the wick assembly after passing through spongemember 80. It has been found that the auxiliary wick is usefulespecially during a short run operation when rotation of the applicatorroll is small and the oil to the wick assembly must be supplemented toequalize the differential supplied during a much longer run. Thus, inthe case of a long run, the oil will be primarily supplied by theapplicator roll through sponge member 80 due to a lag in the capillaryaction of the auxiliary wick. But during a single or shorter run, theoil dispensing level is increased due to oil coated onto the top of theapplicator roll surface by the auxiliary wick and application throughsponge member 80. It is especially important that the main wick notbecome overly saturated with oil and the sponge member accomplishes thispurpose.

By the above invention it has been found that the wick assemblyincluding the sponge providesthe many advantages described above andadditionally minimizes any variation in the oil film being dispensed dueto changes in the oil level in the oil pan. Specifically, due to theconfiguration of the main wick, auxiliary wick,

applicator roll and the unique arrangement of the sponge member, auniform and controlled amount of oil is continuously supplied to theheater fused roll irrespective of changes in the oil level.

While the instant invention as to its object and advantages has beendescribed as being carried in a specific embodiment thereof it is notintended to be limited thereby but it is intended to be covered broadlywithin the scope of the appended claims.

What is claimed is:

1. In a heated pressure roll fusing system for fusing toner imagesproduced by an electrostatic copying machine in which a heated fuserroll disposed below the copy path is coated with an oil to prevent toneroffset, an improved oil dispensing apparatus comprising an applicationroll mounted for rotation in oil for dispensing oil onto the lowersurface of a wicking assembly which is positioned between saidapplicator roll and a heated fuser roll,

a sponge member positioned intermediate said applicator roll surface andwicking assembly to control the flow of oil onto said wicking assembly,

wherein said wicking assembly includes main wick means and auxiliarywick means with said sponge member positioned therebetween,

wherein said auxiliary wick means is positioned in contact with theapplicator roll surface extending from said sponge member to the surfaceof the oil.

fluoro silicone rubber, and urethane rubber.

1. In a heated pressure roll fusing system for fusing toner imagesproduced by an electrostatic copying machine in which a heated fuserroll disposed below the copy path is coated with an oil to prevent toneroffset, an improved oil dispensing apparatus comprising an applicationroll mounted for rotation in oil for dispensing oil onto the lowersurface of a wicking assembly which is positioned between saidapplicator roll and a heated fuser roll, a sponge member positionedintermediate said applicator roll surface and wicking assembly tocontrol the flow of oil onto said wicking assembly, wherein said wickingassembly includes main wick means and auxiliary wick means with saidsponge member positioned therebetween, wherein said auxiliary wick meansis positioned in contact with the applicator roll surface extending fromsaid sponge member to the surface of the oil.
 2. Apparatus according toclaim 1 wherein said sponge member is made of a material selected fromthe group of hexa fluoropropylene vinylidene fluoride, fluoro siliconerubber, and urethane rubber.